Abstract: To permit tests of: ignition timing; dwell angle; engine speed; and voltage levels, a pulse train is provided derived from the ignition system of the engine; the pulse train is applied to a frequency multiplier, preferably a phase locked loop (PLL) which provides a sequence of output pulses having a pulse repetition rate which is a multiple of the frequency of the signals or pulses of the pulse train. An AND gate has the multiplied signals applied thereto and is enabled, selectively, in accordance with the desired test. The output of the AND gate is applied to a counter which counts multiplied pulses within the interval of enabling of the AND gate, the output being applied to a digital indicator to provide a direct readable digital output; preferably, the multiplication rate is selected to provide a digital output indication which is directly readable in desired units.

Abstract: To provide for accurate testing of the performance of automotive vehicles on test stands in which the wheels of the vehicle are in engagement with inertia rollers, the inertia rollers being accelerated through the vehicle wheels by the vehicle engine, and the torque measured, and then decelerated by disconnecting of engine driving power and coasting torque measured, operating parameters related to speed and rate of change of speed are sensed and a speed signal is provided, tractive effort is sensed and a traction signal provided, and the signals are combined to provide an output representative of engine performance, the combined signals being further modified by the output of a correction stage which introduces correction signals such as pressure, ambient temperature, presence or absence of automatic transmission, or the like; the apparatus further comprises selectable switches, for example a speed selector switch, so that measurements can be taken with respect to predetermined design speeds to test performan